Measuring oxygenation changes in tissue as a marker for vascular function

Abstract

A method and system for processing imaging data of a tissue in an individual following a change in oxygenation or blood flow in tissue, for assessing tissue function. Test images are registered with a baseline image, providing registered images. The registered images may be compared to assess variations in the change in the tissue in response to changes in oxygenation or blood flow of the tissue shown in the images. The change in oxygenation or blood flow in the tissue may be quantified and plotted in a parametric plot or displayed in a parametric map to assess whether the change in oxygenation or blood flow, corresponding to a change in signal intensity, is abnormal following a stress event or under other conditions, to assess microvascular or macrovascular function.

What is claimed is: 
     
       1. A method of assessing microvascular or macrovascular function in an individual comprising:
 providing baseline imaging data for displaying a baseline image of tissue; 
 providing test imaging data for displaying a plurality of test images of the tissue, at least a portion of the test imaging data having been acquired while oxygenation or blood flow in the tissue is altered in response to a stress event; 
 registering the test images against the baseline image, providing a plurality of registered images; 
 assessing at least one of oxygenation or blood flow and their changes in the tissue in response to a stress event by comparing the plurality of registered images; 
 wherein an abnormal response to the at least one of oxygenation or blood flow in the tissue is indicative of reduced microvascular or macrovascular function in the tissue. 
 
     
     
       2. The method of  claim 1  wherein providing the baseline imaging data comprises imaging the individual. 
     
     
       3. The method of  claim 1  wherein providing the baseline imaging data comprises accessing stored baseline imaging data of the individual. 
     
     
       4. The method of  claim 1  wherein providing the baseline imaging data comprises imaging the individual prior to the stress event. 
     
     
       5. The method of  claim 1  wherein providing the baseline imaging data comprises imaging the individual at the start of the stress event. 
     
     
       6. The method of  claim 1  wherein providing the baseline imaging data comprises imaging the individual following the end of the stress event. 
     
     
       7. The method of  claim 1  wherein providing the test imaging data comprises imaging the individual following the end of the stress event. 
     
     
       8. The method of  claim 1  wherein the stress event comprises a breathing maneuver by the individual for altering oxygenation of the tissue. 
     
     
       9. The method of  claim 8  wherein the breathing maneuver comprises a breath-hold. 
     
     
       10. The method of  claim 9  wherein the breathing maneuver comprises at least one period of hyperventilation. 
     
     
       11. The method of  claim 9  wherein the breath-hold is voluntary. 
     
     
       12. The method of  claim 9  wherein the breath-hold is induced by a machine. 
     
     
       13. The method of  claim 1  wherein the stress event does not include administration of a vasodilator to the subject. 
     
     
       14. The method of  claim 1  wherein the tissue comprises an organ. 
     
     
       15. The method of  claim 14  wherein the tissue comprises vascular tissue. 
     
     
       16. The method of  claim 14  wherein the vascular tissue comprises a vascular structure within the organ. 
     
     
       17. The method of  claim 14  wherein the organ comprises skeletal muscle. 
     
     
       18. The method of  claim 14  wherein the organ comprises a heart. 
     
     
       19. The method of  claim 18  wherein the baseline image and the test images each comprise images of a portion of a myocardium of the heart. 
     
     
       20. The method of  claim 18  wherein the test images comprise images of at least one cardiac cycle. 
     
     
       21. The method of  claim 20  wherein the registered images comprise registered images based on test imaging data of the heart acquired during a selected period of a cardiac cycle; and comparing the registered images comprises comparing the registered images based on test imaging data of the heart during the selected period. 
     
     
       22. The method of  claim 21  wherein the selected period comprises a relative point in time within the cardiac cycle. 
     
     
       23. The method of  claim 21  wherein the selected period comprises a selected phase of the cardiac cycle. 
     
     
       24. The method of  claim 23  wherein the selected phase comprises systole. 
     
     
       25. The method of  claim 18  wherein the reduced microvascular or macrovascular function comprises heart disease. 
     
     
       26. The method of  claim 25  wherein the heart disease comprises ischemic heart disease, coronary heart disease, heart disease caused by arterial hypertension, diabetes mellitus, hypercholesterolemia, obesity, non-ischemic cardiomyopathies, or myocardial inflammation, congenital heart disease, valvular heart disease, stress-induced cardiomyopathy, microvascular dysfunction or coronary artery stenosis. 
     
     
       27. The method of  claim 1  wherein the baseline imaging data, the test imaging data, or both comprise imaging data acquired by magnetic resonance imaging, nuclear techniques, single-photon emission computed tomography/SPECT, positron emission tomography/PET, computed tomography/CT, echocardiography or other ultrasound, near infrared spectroscopy/NIRS, intravascular blood flow measurements, fractional flow reserve, impedance measurements, or a combination thereof, applied to the tissue. 
     
     
       28. The method of  claim 27  wherein the baseline imaging data, the test imaging data, or both comprise imaging data acquired by blood oxygen level dependent magnetic resonance imaging (BOLD-MRI). 
     
     
       29. The method of  claim 1  wherein the baseline imaging data and the test imaging data each comprise imaging data from a first imaging modality, and further comprising comparing the registered imaging data with imaging data from a second imaging modality. 
     
     
       30. The method of  claim 29  wherein the first imaging modality and the second imaging modality together each comprise magnetic resonance imaging, nuclear techniques, single-photon emission computed tomography/SPECT, positron emission tomography/PET, computed tomography/CT, echocardiography or other ultrasound, near infrared spectroscopy/NIRS, intravascular blood flow measurements, fractional flow reserve, impedance measurements, or a combination thereof. 
     
     
       31. The method of  claim 1  wherein the baseline imaging data and the test imaging data each comprise imaging data from a first imaging sequence, and further comprising comparing the registered imaging data with imaging data from a second imaging sequence. 
     
     
       32. The method of  claim 31  wherein the first imaging sequence and the second imaging sequence are each either BOLD MRI, late contrast MRI, T1 MRI, or T2 MRI. 
     
     
       33. The method of  claim 1  wherein registering the test image against the baseline image comprises automatic registration. 
     
     
       34. The method of  claim 1  wherein registering the test image against the baseline image comprises semi-automatic registration. 
     
     
       35. The method of  claim 1  wherein registering the test image against the baseline image comprises rigid transformation. 
     
     
       36. The method of  claim 1  wherein registering the test image against the baseline image comprises non-rigid transformation. 
     
     
       37. The method of  claim 1  wherein:
 registering the test images against the baseline image comprises:
 segmenting the baseline image for defining at least one region of interest of the tissue, resulting in a segmented baseline image; 
 segmenting the test images for defining the at least one region of interest in each of the test images, resulting in segmented test images; and 
 registering the segmented test images with the segmented baseline image for registering the at least one region of interest in the segmented test images with the at least one region of interest in the segmented baseline image, resulting in a plurality of segmented registered images; 
 
 comparing the plurality of registered images comprises comparing the segmented registered images for assessing at least one of oxygenation or blood flow in the at least one region of interest; and 
 the abnormal response or cyclic pattern of the at least one of oxygenation or blood flow in the tissue corresponds to the at least one region of interest and is indicative of reduced microvascular or macrovascular function in the tissue in the at least one region of interest. 
 
     
     
       38. The method of  claim 37  wherein segmenting the baseline image and the test image comprises automatic segmentation. 
     
     
       39. The method of  claim 37  wherein segmenting the baseline image and the test image comprises semi-automatic segmentation. 
     
     
       40. The method of  claim 1  wherein comparing the plurality of registered images comprises generating a parametric plot of at least one organ parameter for the tissue. 
     
     
       41. The method of  claim 1  wherein comparing the plurality of registered images comprises a pixel-by-pixel analysis to generate a parametric map of at least one parameter relevant to the tissue of interest. 
     
     
       42. The method of  claim 1  wherein comparing the plurality of registered images comprises comparing a signal intensity. 
     
     
       43. The method of  claim 1  wherein the abnormal response comprises a blunted increase, a lack of increase, a blunted decrease, a lack of decrease, or an abnormally strong decrease. 
     
     
       44. The method of  claim 1  further comprising segmenting the registered images for defining the at least one region of interest in each of the registered images, resulting in segmented registered images; and wherein
 comparing the plurality of registered images comprises comparing the segmented registered images for assessing at least one of oxygenation or blood flow in the at least one region of interest; and 
 the abnormal response to the at least one of oxygenation or blood flow by the tissue corresponds to the at least one region of interest and is indicative of reduced microvascular or macrovascular function in the tissue in the at least one region of interest. 
 
     
     
       45. The method of  claim 44  wherein comparing the plurality of registered images comprises comparing a signal intensity of the entire at least one region of interest. 
     
     
       46. A non-transitory computer readable medium having instructions encoded thereon executable by a processor to cause the processor to perform a method comprising:
 receiving baseline imaging data for displaying a baseline image of tissue; 
 receiving test imaging data for displaying a plurality of test images of the tissue, at least a portion of the test imaging data having been acquired while oxygenation or blood flow in the tissue is altered in response to a stress event; 
 registering the test images against the baseline image, providing a plurality of registered images; 
 assessing at least one of oxygenation or blood flow in the tissue in response to a stress event by comparing the plurality of registered images; and 
 wherein an abnormal response of the at least one of oxygenation or blood flow in the tissue is indicative of reduced microvascular or macrovascular function in the tissue.